The design of the network formation and degradation processes is required to control hydrogel's life cycle. There have been many studies to optimize both processes of the hydrogel for biomaterials. The conventional studies based on the assumption that the network formation and degradation processes are equivalent. The premise of the similarity is not self-evident, which is diffi cult to investigate experimentally. It is because of the diffi culty in the experimental determination of the connectivity of the network. In this study, we utilized the Tetra gel with slow degradation units to observe a continuous process from network formation to degradation of a single hydrogel. We measured the time-development of the linear viscoelastic properties during the network formation and degradation processes using a single system. The linear viscoelasticity at the same connectivity and the critical points for gelation and degradation well agreed. These results strongly suggest that the network formation and degradation go along the identical path toward the opposite directions. Based on our fi ndings, we propose a simplifi ed criterion for the gelation over the Winter-Chambon criterion based on the observation. These fi ndings will help a basis for the sol-gel transition behavior of the polymer gels.

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In order to evaluate the safety of steel structures quantitatively, it is important to understand the effect of material property variations on steel member performance. This paper investigates the mean and variance of steel member resistance and deformation capacities while considering the stochastic properties of material properties, such as yield stress, tensile strength, and other factors. The analytical methods employed in the paper are the finite element method (used for the calculation of elastic-plastic behavior of steel beams) and the Monte Carlo simulation method (used for the stochastic calculation). Based on the analytical results, the paper proposes stochastic tri-linear loaddeformation relationship models for H-shaped steel beams that are applicable to the reliability analysis of steel frame structures.

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